Has.Property cannot see explicit interface implementation properties

[yaakov-h]

Using nunit.framework 3.2 and nunit3-console 3.0.1.

Code:

using NUnit.Framework;

namespace NUnitHasProperty
{
    public interface IFoo
    {
        string Description { get; }
    }

    public class ImplicitFoo : IFoo
    {
        public string Description => "Foo";
    }

    public class ExplicitFoo : IFoo
    {
        string IFoo.Description => "Foo";
    }

    [TestFixture(typeof(ImplicitFoo))]
    [TestFixture(typeof(ExplicitFoo))]
    public class HasPropertyTestCase<TFoo>
        where TFoo : IFoo, new()
    {
        [Test]
        public void DescriptionIsFoo()
        {
            IFoo thing = new TFoo();
            Assert.That(thing, Has.Property(nameof(IFoo.Description)).EqualTo("Foo"));
        }
    }
}

Results:

NUnit Console Runner 3.0.5813
Copyright (C) 2015 Charlie Poole

Runtime Environment
   OS Version: Microsoft Windows NT 10.0.10240.0
  CLR Version: 4.0.30319.42000

Test Files
    NUnitHasProperty.dll


Errors and Failures

1) Error : NUnitHasProperty.HasPropertyTestCase<ExplicitFoo>.DescriptionIsFoo
System.ArgumentException : Property Description was not found
Parameter name: name
   at NUnit.Framework.Constraints.PropertyConstraint.ApplyTo[TActual](TActual actual)
   at NUnit.Framework.Assert.That[TActual](TActual actual, IResolveConstraint expression, String message, Object[] args)
   at NUnit.Framework.Assert.That[TActual](TActual actual, IResolveConstraint expression)
   at NUnitHasProperty.HasPropertyTestCase`1.DescriptionIsFoo() in C:\temp\NUnitHasProperty\NUnitHasProperty\HasPropertyTestCase.cs:line 29

Run Settings
    WorkDirectory: C:\temp\NUnitHasProperty\NUnitHasProperty\bin\Debug
    NumberOfTestWorkers: 12

Test Run Summary
    Overall result: Failed
   Tests run: 2, Passed: 1, Errors: 1, Failures: 0, Inconclusive: 0
     Not run: 0, Invalid: 0, Ignored: 0, Explicit: 0, Skipped: 0
  Start time: 2016-04-06 04:58:54Z
    End time: 2016-04-06 04:58:54Z
    Duration: 0.085 seconds

Results (nunit3) saved as TestResult.xml

[CharliePoole]

Are you sure this is not an artifact of using nameof in the code rather than a string?

[yaakov-h]

Yes. If I add the following test, then I now have 3 passing and 1 failing - failing one is as above.

[Test]
public void NameOfIFooDescriptionIsDescription()
{
    Assert.That(nameof(IFoo.Description), Is.EqualTo("Description"));
}

[rprouse]

I have confirmed this issue and confirmed that it has nothing to do with the nameof operator.

[mjedrzejek]

Maybe this is not a real case, but if this is an issue, what should be the result in case of a class which have property Description implemented twice (explicit and implicit):

    public class FooBar : IFoo
    {
        public string Description => "Foo";
        string IFoo.Description => "Bar";
    }

Should we check both properties?

[yaakov-h]

Good question. For another example, everything that implements IEnumerable<T> does this - one IEnumerator<T> GetEnumerator() from IEnumerable<T> and one IEnumerator GetEnumerator() from IEnumerable.

[CharliePoole]

All of this will remain somewhat adhoc so long as we are not passing through the types of the supplied arguments but are converting them to objects. Once we have actual types - probably through use of generic methods - we would want to use the appropriate interfaces implemented for those types. That is, if an interface is passed we would use the explicit implementation, otherwise we wouldn't.

For now, we are forced to do the best we can using some sequence of searching for appropriate implementations.

[rprouse]

From @NUnitTester, this also causes Count to not be found where an array is cast to an ICollection because arrays explicitly implement ICollection.

From #1816

ICollection<int> numbersCollection = IWorker.DoMethod();
Assert.That(numbersCollection, Has.Count.EqualTo(3));

Think about the following usecase: You will test different implementations of IWorker given as parameter of tha attribute TestFixture, in my case 3. Two will use an Array to give back as ICollection and one will give back an HashSet.
How to write the Unit-Test with Has.Count or Has.Length?

And don't answer to use Is.EqualTo ... I know it.